Photographic elements containing fogged and unfogged silver halide grains and a slow silver halide emulsion layer

ABSTRACT

Improved photographic elements comprising fogged and unfogged silver halide grains and a slow speed sliver halide emulsion layer exhibiting improved antifoggant properties in developer solutions are disclosed. Still another object of this invention is to provide improved photographic elements comprising surface latent image iodidecontaining silver halide grains and fogged internal latent image silver halide grains.

United States Patent Joseph R. Ditzer, Jr.

Kingsport, Tenn.;

Fred W. Spengler, Rochester, N.Y. 722,223

Apr. 18, 1968 Sept. 21, 1971 Eastman Kodak Company Rochester, N.Y.

Inventors Appl. No. Filed Patented Assignee PHOTOGRAPIIIC ELEMENTS CONTAINING FOGGED AND UNFOGGED SILVER HALIDE GRAINS AND A SLOW SILVER HALIDE EMULSION LAYER 11 Claims, No Drawings US. Cl 96/67, 96/68, 96/69 Int. Cl G03c 1/76, G030 3/00 Field of Search 96/68, 67, 69, I09

Primary Examiner-Norman G. Torchin Assistant ExaminerM. F. Kelley Atrorneys-W. H. J. Kline and Bernard D. Wiese ABSTRACT: Improved photographic elements comprising fogged and unfogged silver halide grains and a slow speed silver halide emulsion layer exhibiting improved antifoggant properties in developer solutions are disclosed.

PHOTOGRAPIIIC ELEMENTS CONTAINING FOGGED AND UNFOGGED SILVER HALIDE GRAINS AND A SLOW SILVER HALIDE EMULSION LAYER BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to photographic materials, their preparation, and use. In one aspect, this invention relates to a photographic element comprising fogged internal image silver halide grains, unfogged surface latent image grains and an unfogged fog-inhibiting layer, which element exhibits good fogresistance on development. In another aspect, this invention relates to a photographic element imparting fog reduction in developer solutions and comprising layers having fogged internal latent image grains, unfogged surface latent image grains and a silver halide emulsion layer comprising silver halide grains exhibiting photographic sensitivity which is substantially lower than the sensitivity of the unfogged surface latent image grains.

2. Description of the Prior Art Fog, the more or less intense blackening of an emulsion, has its source in the very nature of the silver halide emulsion, but may also be caused through prolonged development, aerial oxidation, aging, and other physical factors such as light reflection on lens surfaces. The most common source of fog observed is caused by the presence of reduced silver in the silver halide grains which are spontaneously developable without exposure to light. This fog occurs in the emulsion and invariably is produced upon development of the light-sensitive element for an extended period of time. In fact, it is well known that any unexposed silver halide-containing element, left in a fresh developer solution will turn black after an extended period of time.

It has now been observed that in developing the elements described in Luckey & Hoppe U.S. Pat. No. 2,996,382 in certain photographic developing processes, for example those where containers of developer are used continuously or where developers are not replenished or changed for long periods of time, an unusual amount of fog is detected in the elements so processed. This fog is far greater than that normally expected of the emulsions and it appears that these continuous or partially exhausted developer systems contain certain fogproducing substances such as iodide ions which are not present in fresh developers.

Among the most common antifoggants used to reduce fog to tolerable limits are soluble bromides, iodide ions and chloride ions, the latter used on silver chloride emulsions (Mees, The Theory of the Photographic Process, page 344). In developing the elements of Luckey & Hoppe cited previously, we have found, however, that iodide ions in the developer do not act as an antifoggant but cause an increase in fog.

It is known that silver halide crystals of the type employed in photographic emulsions have both surface and internal light sensitivity and that these types of sensitivity can vary considerably among different emulsions. Silver halide grains having a high ratio of surface-to-internal sensitivity comprise the silver halide grains used in the majority of photographic emul SlOl'lS. V M

It is also known that in using the combination of various surface latent image grains with various internally fogged latent image grains, the sensitivity and contrast characteristics of such combination is substantially greater than those obtained from either type of grain alone in a photographic emulsion (see Luckey et al. US. Pat. No. 2,996,382 issued to 15, 1961). However, photographic emulsions containing such a combination of grains tend to produce fog upon development and more particularly in those continuous processing tanks or developer baths described above.

Even where known antifoggants have been employed in the elements described above, considerable fog is still produced using continuous development solutions, however.

It is evident therefore that the art would be enhanced by photographic elements and photographic silver halide grain combinations and emulsion systems which exhibit reduced fog and which impart improved fog resistance to elements developed in continuous or partially exhausted developing solutions.

Accordingly, it is an object of this invention to provide photographic materials which exhibit an improved combination of properties.

Another object of this invention is to provide photographic elements which exhibit high sensitivity and contrast and have improved fog resistance upon development in continuous developer systems.

Still another object of this invention is to provide improved photographic elements comprising surface latent image iodide-containing silver halide grains and fogged internal latent image silver halide grains.

Other objects will become apparent from a consideration of the following specification and claims.

SUMMARY OF THE INVENTION In accordance with this invention, there is now provided im proved means for reducing fog and speed loss upon development of a photographic element and more particularly in a continuous or partially exhausted developing solution system. This element comprises a support, unfogged surface latent image iodide-containing silver halide grains adjacent to fogged internal latent image silver halide grains and layer (1) comprising unfogged silver halide grains in which said halide comprises less than about 10 mole percent iodide and having photographic surface sensitivity which is less than about onetenth that of said surface image silver halide grains.

The substantially iodide-free layer (I) has a relatively slower speed or surface sensitivity than the surface image silver halide grains. By slower speed is meant that relatively no visible image is produced in said layer upon exposure and development of the unfogged surface latent image silver halide grains. This layer (I) preferably comprises at least about 30 to about 65 mole percent chloride the remainder being bromide.

The silver halide grains used in this invention in other than layer (I) can thus comprise blends or mixtures of unfogged iodide containing surface image grains and fogged internal image grains, or these two types of grains can be coated in discrete layers which are in close proximity, i.e., in contiguous layers of the photographic element. In coating the various types of grains in separate layers, any one of the emulsion layers can be coated on top, since the fogged internal image grains in emulsion form or the slower speed layer have sufficient transparency to enable the surface image grains to be placed closest to the support and still receive sufficient transmitted radiation for exposure. Exposure of the unfogged surface image grains placed closest to the support can also be made through the support where this is transparent. However, for convenience of processing, thesurface image grains are preferably coated over the fogged internal grains. Alternatively, two types of the above grains, i.e., surface image and internal image, can be mixed as a blend and coated over an emul sion layer, comprising for example, fogged internal image grains identical to or different from the fogged internal image grains in the blend. The slow-speed layer having from less than about 10 mole percent iodide, e.g. 0 to about 10 mole percent iodide can thus be disposed in virtually any position on the element except between said other two types of grains. For exam ple, said layer can be above the support and beneath said two types of grains in emulsion or layer form or the like or above said two grain types or blends thereof. In one preferred arrangement, the slower speed layer is placed directly adjacent to and beneath said fogged internal image grains. It is to be understood that various other layers can be intermediate to these layers and grains. Said intermediate layers can comprise subbing layers, protective layers and the like.

The unfogged light-sensitive silver halide layer is substantially slower in speed, i.e. less sensitive, than the higher speed surface image silver halide grains. By substantially slower is meant at least about one-tenth and preferably about one-hundredth of said higher speeds. However, it can be even less sensitive if desired. it will be understood by those skilled in the art that the combination of grains in emulsion layers and blends thereof as described above provide speed increases when processed in developers being moderately high in silver halide solvent action as well as in developers having little or no silver halide solvent activity. However, in our improved combination, the higher the iodide concentration in the developer solution combination, the greater the fog inhibiting effect as shown by the examples below. In addition, speed increases of the surface latent image grains can be effected by the use of various addenda as set forth hereinafter.

The surface latent image grains used in the practice of this invention have a relatively high degree of surface sensitivity and relatively low internal sensitivity and contain about 0.5 to about 99 mole percent iodide while the internal image grains used have a high degree of internal sensitivity but relatively low surface sensitivity. The surface latent image grains contain silver halide grains that have substantial surface sensitivity and form latent images on the surface thereof when exposed to light. Unlike the fogged silver halide internal latent image grains described herein, the surface latent image silver halide grains are substantially unfogged. The photographic silver halides which can be used in the preparation of the surface latent image grains include, for example, silver bromiodide, silver chloroiodide, silver chlorobromoiodide, and the like, the preferred halide being bromoiodide. For a description of suitable grains and emulsions that form latent images on the surface of the silver halide grains, reference is made to Trivelli and Smith in-The Photographic Journal, Volume LXXX, July 1940, (pages 285-288). Typically, such grains and their emulsions are those which, when measured according to normal photographic testing techniques by coating a test portion of the emulsion on a transparent support, exposing the test portion to a light intensity scale for a fixed time between 0.01 and 1 second and development for 6 minutes at 68 F. in Developer A as hereinafter defined, have a sensitivity, measured at a density of 0.1 above fog, greater than the sensitivity of an identical test portion of the same emulsions which has been exposed in the same way, bleached minutes in aqueous 0.3 percent potassium ferricyanide solution at 65 F., and developed for 5 minutes at 65 F. in Developer B as hereinafter defined. Developer A is the usual type of surface image developer and Developer B is an internal developer having high silver halide solvent activity.

The degree of internal sensitivity of the surface latent image grains is subject to wide variation. The surface latent image grains and their emulsions can have relatively little internal sensitivity or they can have a fair amount of internal sensitivity, but preferably not greater than the surface activity. The surface latent image grains can have high or low contrast since useful effects can be obtained with both types of emulsions. The surface latent image grains can also be characterized as having a Dmax. greater than about 0.50 when coated at a coverage of about 540 mg. silver per square foot, exposed to a step wedge and processed for 12 minutes in Developer C as hereinafter define. Particularly good results are obtained with surface image silver iodo-halide surface latent image grains such as silver bromoiodide emulsions. Such emulsions can contain varying concentrations of iodide although especially useful results are obtained with such iodo-halide surface latent image grains containing from about 0.5 to about mole percent iodide.

The internal latent image photographic silver halide grains employed in the practice of this invention contain fogged internal latent image silver halide grains. Any of the photographic silver halides can be used in the preparation of these internally fogged grains and include, for example, silver bromide, silver chlorobromoiodide, silver chlorobromide, silver chloride and the like. For a description of suitable grains that form latent images internal to the silver halide grains reference is made to Davey and Knott US. Pat. No.

2,592,250, issued Apr. 8, 1952, Luckey and Hoppe U.S. Pat. No. 2,996,382, issued Aug. 15, 1961 and Luckey and Hoppe US. Pat. No. 3,178,282, issued Apr. 13, 1965. Typically, such grains and their emulsions are those which, when measured according to normal photographic techniques in their unfogged state by coating a test portion of the emulsion on a transparent support, exposing to a light intensity scale having a fixed time between 0.1 and 1 second, bleaching 5 minutes in 0.3 percent potassium ferricyanide solution at 65 F. and developing for about 5 minutes at 65 F. in Developer B described hereinafter, have a sensitivity measured at a density of0.1 above fog appreciably greater (for example, at least 1.4 Log E greater) than the sensitivity of an identical test portion which has been exposed in the same way and developed for 6 minutes at 68 F. in Developer A described hereinafter. The internal image grains employed in the practice of this invention are fogged partly or completely before use. The fogging is generally sufficient to give a density of at least 0.50 when one mole (AgX) of the fogged emulsion is coated in a blend with 3 moles of surface image emulsion at a total coverage of about 540 mg. of silver per square foot and processed for 5 minutes in Developer B hereinafter described. The surface Dmax. of the fogged internal image emulsions is generally less than about 0.30 when the emulsions are exposed to Dmax. and processed for 8 minutes in Developer C identified hereinafter.

The fogging of the internal image grains used in this invention can be effected using any method suitable for this purpose. For example, such fogging can be accomplished by exposing the grains to light. Other methods such as chemical fogging methods can also be used. The photographic silver halide grains having high internal fog but low surface sensitivity can also be prepared by fogging grains having both internal and surface sensitivity and then bleaching the surface image with a solution of potassium ferricyanide. Another means of obtaining the fogged internal image grains is by exposure of nonfogged internal image grains to high energy radiation, such as X-rays.

The ratio between the surface latent image grains and the fogged internal image grains can be varied, depending upon the types of grains used, the contrast of the emulsions and other known variables. In general, quite useful results are obtained in those cases where the molar ratio of the surface image emulsion is at least equal to or greater than that of the fogged internal image grains. Useful results can be obtained even where the molar ratio, as explained above, is 42:1. Where the molar percent of the fogged internal image grains exceeds that of the surface image grains, such as 1:3 ratio,

' there can be some loss of speed, although the contrast of the combination is considerably greater than that of the surface latent image emulsion. Accordingly, useful results can be obtained where the molar ratio of surface to fogged internal image grains varies from about 42:1 to 1:3. in a like manner, the ratios of the unfogged surface latent image grains as compared to the slow-speed light-sensitive layer can vary from 20:1 to 1:1 and useful results are likewise still attained.

The following developing solutions are referred to hereinabove.

Sodium sulfite, desiccated 30.00 Hydroquinone 2.50 Sodium Meluborate 10.00 Potassium bromide 0.50

Wuterto make 1 liter The silver halide emulsions of a photographic element useful in this invention can contain conventional addenda such as gelatin plasticizers, coating aids, antifoggants such as the uzaindines and hardeners such as aldehyde hardeners, e.g., formaldehyde, mucochloric acid, glutaraldehyde bis (sodium bisulfite), maleic dialdehyde, aziridines, dioxane derivatives, oxypolysaccharides and vinyl sulfonyl ethers. Sensitizing dyes useful in sensitizing such emulsions are described, for example, in U.S. Pats. Nos. 2,526,632 of Brooker and White issued Oct. 24, 1950, and 2,503,776 of Sprague issued Apr. 11, 1950. Spectral sensitizers which can be used are the cyanines, merocyanines, complex (trinuclear) cyanines, complex (trinuclear) merocyanines, styryls, and hemicyanines. Developing agents can also be incorporated into the silver halide emulsion if desired or can be contained in a separate underlayer.

The silver halide emulsion layers of a photographic element which are useful in the instant invention can contain any of the hydrophilic, water'permeable binding materials suitable for this purpose. Suitable materials include gelatin, colloidal albumin, polyvinyl compounds, cellulose derivatives, acrylamide polymers, etc. Mixtures of these binding agents can also be used. The binding agents for the emulsion layer of the photographic element can also contain dispersed polymerized vinyl compounds. Such compounds are disclosed, for example, in US. Pats. Nos. 3,142,568 of Nottorf issued July 28, 1964; 3,193,386 of White issued July 6, 1965; 3,062,674 of I-louck, Smith and Yudelson issued Nov. 6, 1962; and 3,220,844 of Houck, Smith and Yudelson issued Nov. 30, 1965; and include the water-insoluble polymers of alkyl acrylates and methacrylates, acrylic acid, sulfoalkyl acrylates or methacrylates and the like.

The silver halide emulsion layers of a photographic element which are useful in the instant invention can be coated on a wide variety of supports. Typical supports are cellulose nitrate film, cellulose ester film, polyvinyl acetal film, polystyrene film, poly(ethylene terephthalate) film and related films or resinous materials as well as glass, paper, metal and the like. Supports such as paper which are coated with a-olefin polymers, particularly polymers of a-olefins containing two or more carbon atoms, as exemplified by polyethylene, polypropylene, ethylene-butene copolymers and the like can also be employed.

The speed of the photographic silver halide grains and their emulsions useful in the instant invention can be further increased by including in the emulsions a variety of hydrophilic colloids such as carboxymethyl protein of the type described in U.S. Pat. No. 3,011,890 of Gates, Jr., Miller and Koller issued Dec. 5, 1961, and polysaccharides of the type described in Canadian Pat. No. 635,206 of Koller and Russell issued Jan. 23, 1962.

Photographic silver halide grains and emulsions useful in the instant invention can also contain speed-increasing compounds such as quaternary ammonium compounds, polyethylene glycols or thioethers. Frequently, useful effects can be obtained by adding the aforementioned speed-increasing compounds to the photographic developer solutions instead of, or in addition to, the photographic emulsions.

The photographic elements prepared according to the instant invention can be used in various kinds of photographic systems. In addition to being useful in X-ray and other nonoptically sensitized systems, they can also be used in orthochromatic, panchromatic and infrared sensitive systems. The sensitizing addenda can be added to photographic systems before or after any sensitizing dyes which are used.

The invention can be used in emulsions intended for color photography, for example, emulsions containing color-forming couplers or emulsions to be developed by solutions containing couplers or other colorgenerating materials, emulsions of the mixed-packet type such as described in U.S. Pat No. 2,698,794 of Godowsky issued Jan. 4, 1955; in silver dyebleach systems; and emulsions of the: mixed-grain type such as described in U.S. Pat. No. 2,592,243 ofCarroll and Hanson issued Apr. 8, 1952.

Silver halide emulsions useful in the instant invention can be chemically sensitized using any of the well-known techniques in emulsion making, for example, by digesting with naturally active gelatin or various sulfur, selenium, tellurium compounds and/or gold compounds. The emulsions can also be chemically sensitized with salts of noble metals of group VIII of the periodic table which have an atomic weight greater than 100.

The improvements in fog-reduction without significant loss of speed obtained by the inclusion of the fog-inhibiting, slowspeed, unfogged silver halide layer disclosed herein is further illustrated by the following examples of preferred embodiments of the invention although it will be understood that these examples are included merely for purposes of illustration and are not intended to limit the scope of the invention unless otherwise specifically indicated.

EXAMPLE 1 COATING On a polyethylene terephthalate film support is coated a clear gelatin layer. Over this is coated fogged internal image gelatino chlorobromide grains in the form of an emulsion layer (164 mg. Ag/ft?) containing 50 mole percent chloride, 50 mole percent bromide and prepared in the manner as disclosed in Luckey & Hoppe U.S. Pat. No. 2,996,382 issued Aug. 15, 1961, example 4. On the prefogged layer is then coated high'speed sulfur-gold sensitized silver gelatino bromoiodide grains having a 5 mole percent iodide in the form of an emulsion layer concentration at 450 mg. Ag./ft. This layer has a high surface sensitivity and a low internal sensitivity and is of the type disclosed in Luckey et a1. (supra), example 1.

EXAMPLE 2 COATING A second coated sample is prepared as in example 1 except that a relatively light-insensitive silver chlorobromide gelatin emulsion having 40 mole percent chloride is coated in place of the gelatin underlayer at mg. Ag/ft".

EXAMPLE 3 COATING A third coating sample is prepared as in example 1 except that a chlorobromide emulsion having 40 mole percent chloride is coated in place of the gelatin underlayer at a coverage of 50 mg. Ag/ft In each of the above examples, the coatings are exposed on an Eastman 1B sensitometer and developed for 2 minutes at 98 F. in a series of surface image developers having the following formula and containing various concentrations of soluble iodide which approximate the iodide buildup in a partially exhausted developer solution.

20 Grams Hydroquiinone 50 Grams Sodium sulfite (anhydrous) 15 Grams Glutaraldehyde bisulfite 15 Grams Potassium bromide 1 Gram l-Phenyl-B-pyrazolidone 31.25 m1. Diethyl glycol containing 0.2 gram sodium anthraquinone sulfonate 15-18 Grams Sodium metaborate 41-1 0 adjusted to pH 9.5

H 0 added to make 1 liter After fixing and drying the following results are obtained:

Potassium lodide Concentration Gross Relative in Mg/liter Fog Speed Gamma Example l Coating: 0-2l 100 2.0 30 0.28 148 1.7 60 0.5l 1 l0 L7 120 0.76 95 L3 Example 2 Coatings 0 0.24 NS L6 30 0.2l I20 1.6 60 0.20 I 1.7 I20 0.20 9] 1.8 Example 3 Coatings 0 0.24 97 1.9 30 0.221 15 L8 60 0.22l32 1.9

It is also observed that by positioning the fog-inhibiting, silver halide iodide-free layer above the internally fogged latent image and the unfogged surface latent image layer similar improved reduction in fog is noted coupled with a stable gamma and D Although the invention has been described in considerable detail with particular reference to certain preferred embodiments thereof, it will be understood that variations and modifications can be effected without departing from the spirit and scope of the invention as described hereinbefore and as defined in the appended claims.

We claim:

I. A photographic element'comprising a support, unfogged surface latent image iodide-containing silver halide grains adjacent to fogged internal latent image silver halide grains, and a separate layer (1) comprising unfogged silver halide grains in which said halide comprises less than about 10 mole percent iodide and having photographic surface sensitivity which is less than about one-tenth that of said surface image silver halide grains, said layer l) disposed other than between said unfogged surface latent image iodide-containing silver halide grains and said fogged internal latent image silver halide grains.

2. A photographic element of claim 1 in which said unfogged surface latent image iodide-containing silver halide grains and said fogged internal latent image silver halide grains are each in discrete layers.

3. A photographic element of claim 1 in which said unfogged surface latent image iodide-containing silver halide grains and said fogged internal latent image silver halide grains are in one layer.

4. A photographic element of claim 1 in which said unfogged surface latent image iodide-containing silver halide grains and said fogged internal latent image silver halide grains are each in discrete layers farther from said support than said layer (1).

5. A photographic element of claim 1 in which said unfogged surface latent image iodide-containing silver halide grains and said fogged internal latent image silver halide grains are in one layer adjacent to said layer (I).

6. A photographic element of claim 1 in which said unfogged surface image iodide-containing silver halide grains contain about 0.5 to about 10 mole percent iodide.

7. A photographic element of claim 6 in which the halide in said silver halide grains in layer (I) is at least about 30 mole percent chloride.

8. A photographic element of claim 1 in which said unfogged surface latent image iodide-containing grains and certain of said fogged internal latent image silver halide grains are in one layer and certain of said fogged internal latent image silver halide grains are in another layer other than layer (I).

9. The element of claim 8 in which layer (1) is disposed closer to said support than are said fogged grains.

10. The element of claim 1 in which said surface latent image iodide-containing silver halide grains are chemically and spectrally sensitized.

11. The element of claim 8 in which said layer (I) is farther from said support than are said fogged grains. 

2. A photographic element of claim 1 in which said unfogged surface latent image iodide-containing silver halide grains and said fogged internal latent image silver halide grains are each in discrete layers.
 3. A photographic element of claim 1 in which said unfogged surface latent image iodide-containing silver halide grains and said fogged internal latent image silver halide grains are in one layer.
 4. A photographic element of claim 1 in which said unfogged surface latent image iodide-containing silver halide grains and said fogged internal latent image silver halide grains are each in discrete layers farther from said support than said layer (I).
 5. A photographic element of claim 1 in which said unfogged surface latent image iodide-containing silver halide grains and said fogged internal latent image silver halide grains are in one layer adjacent to said layer (I).
 6. A photographic element of claim 1 in which said unfogged surface image iodide-containing silver halide grains contain about 0.5 to about 10 mole percent iodide.
 7. A photographic element of claim 6 in which the halide in said silver halide grains in layer (I) is at least about 30 mole percent chloride.
 8. A photographic element of claim 1 in which said unfogged surface latent image iodide-containing grains and certain of said fogged internal latent image silver halide grains are in one layer and certain of said fogged internal latent image silver halide grains are in another layer other than layer (I).
 9. The element of claim 8 in which layer (I) is disposed closer to said support than are said fogged grains.
 10. The element of claim 1 in which said surface latent image iodide-containing silver halide grains are chemically and spectrally sensitized.
 11. The element of claim 8 in which said layer (I) is farther from said support than are said fogged grains. 